Telescopic shock absorbing strut



1 J. MERCIER TELESCOPIC SHOCK ABSORBING STRUT Oct. 9, 1951 5 Sheets-Sheet 1 Filed Feb. 24, 1948 5 Sheets-Sheet 2 Filed Feb. 24, 1948 Jsmv MERCIEB a) W QM Hrromvey:

J. MERCIER v TELESCOPIC SHOCK ABSORBING STRUT Oct. 9, 1951 5 Sheets-Sheet 5 Filed Feb. 24, 1948 Lvvawraz Jew/v R 15 Oct. 9, 1951 J. MERCIER TELESCOPIC SHOCK ABSORBING STRUT 5 Sheets-Sheet 4 Filed Feb. 24, 1948 INVENI'OR JEWA/ MEEc-IEE M flr'rmeueyg- Hill Wili

Patented Oct. 9, 1951 UNITED STATES PATENT OFFICE 2,570,362 i t v H TELESCOPIC SHOCK ABsonnmG STRIl' I Jean Mercier, Paris, France I V Application February 24, 1948; Serial No. 10,504

In France May18, I946I' I Section 1, Public Law 690, August 8, 1946 1 Patent expires May 18, 1966.,

5 Claims. I (01. 267 64).

sorbers, more. particularly tov shock absorbing,

struts used in undercarriages of airplanes as landing gear. These shock absorbers, to meet the conditions required, must possess a some special features. When the airplanelands, the shock absorber mus t..be able to absorb the impact dueto the shockof the landing. For that purpose, it must present a substantial resistance to the inward thrust ,of the movable member. 0n the other hand, after this impact has been absorbed, and while the airplane is rolling along on the ground, the shock absorber must be suf-v ficiently responsive to absorb the shocks due to the roughness of the ground, without transmittin them to the airplane. V

Numerous devices have heretofore been provided which allow the operating of the shock absorber under two different conditions. These prior systems, however, are rather complicated, and furthermore do not-satisfactorily meet, the

conditions which, are encountered:

The purpose of the present invention isr to avoid the drawbacks, of prior devices, and to provide a suspension .which will meet the required operating conditions. I

The shock absorber according to the present invention is. of the type including a, variable volume chamber, a constant volume chamber, andfmeans intended to establish and to close communication between these two chambers under determined conditions. a I

According to a first feature of the present invention, the means of communication include at least one passage closed by a check-valve arranged in such a way that its face opposite the face on which the overpressure is applied, is submitted first to the pressure of a calibrated spring, and second, to a variable pressure, means j slides in a closed chamber communicating with the surrounding space only through a compensating opening of small section. I I I With such an arrangement, when the shock absorber receives the impact of landing, the

check-valve opens itself for a pressure determined by thev calibration of the spring added to thep ressure existing above the piston integral with the check-valve and. which is equal to the vera e pressureinwardseizistingfrom the chain;

h Wi ifll Q fi c e kz a e.

The checkvalveis connected with its piston,

situated abovethe ,piston of the check-valve communicating withthe face of the check-valve which is submitted to the overpressure on its upstream face, to an opening controlled by a check valve which opens towards the region of overpressure. Thus, when the shock absorber slackens. after landing, the underpressure which occurs, upstream from the check valve of the shock absorber has for a result to remove from its seat the inner check valve of the rod and to suc k up the .a ir o rv the gas which are in the closed chamber. situated above the piston of the, check-valve. I I, I I l I A fall of pressure is thus caused in the chamber-so that while. the airplane is rolling along on the ground, the checlsfvalve of the shock absorber opensunder application of a pressure equal tothe calibration of the spring added to the pressure thus reduced. This pressure tends to increase progressively by the infiltration of. air or gas through the, compensation aperture'.; However, by the successive recoils which are close together, the underpressure is restored and even. increased by the pumping efiects corresponding? to each way down-of the valve of the shock absorber. It can thus be seen that by the means of this arrangement,the shock absorber according to the present invention presents a substantial resistance to the thrusting force of the movable member under the landing. shock, and asubstantially reduced resistance while the airplane is rolling along on the ground. f

According to a preferred embodiment of the present invention, the diameter of the piston T which is'integral with the valve is equalto the diameter of the surface of the valve to which the overpressure is applied. The valve thusbecomes completely free from the average pressure existing in the chambertoward which the valve opens. In some cases, however, it may be ad vantageous to let the average pressure of the chamber toward which the valve opens, act under determined conditions on the valve. For that purpose, a slightly smaller section can, in. that case, be given to the piston, according to. the operating conditions to be met, than that of the surface of the valve to which the overpressure is applied. I

It will be realized that whichever maybe the case elected of the three gdiameter of the pisthe check-valve is=shut,1so that it :does not enpere,

ate at the landing nor during the rolling of the 'flirplaneromthe ground. 7 w

- According still to:another L-feature 10f the pres ent invention, it is. designedtocomplete ithashock absorber by another passage, provided in .the means of communication :between the chambers and intended toflmake .easier the lengthening (Of the :shock absorber :after its suddenshorltening due :to the landing shock, intendedato give it back into .eoptimum :properties .in case of recoil :of. the airplane on thegron-nd. .EFor that purpose, ;.according. to the present invention, this passage is controlled :by a check-valve opening towards the space. iof variable :volume :and urged towards its seat-:by a spring decreasing the recoil andthe strength of which balances, for instance, theipressure corresponding to the weight .of the airplane- Inxzthat way, :the check valve .is normally :shut but litiopens under the heavy pressure established lathe shockiabsorberafiter the landinssh ok nd allows the fluid to flow towards the chamber of variable yolume till he aboyeementioned pressure iare chedratwhichtimeitshuts,

111% invention will be better understo d by the aid of the ioined drawi gs on wh ch ha e bee represent d as -.e2. .amr es pa ic ar em o iments oi the invention a the d awings:

Fig. 1 is an axial sectional ashockabsorber according to the present invention;

Fig. 2 is a similar View of a more elaborate embodiment of the shock absorber of Fig. .1;

\Fig. 3 is a section on the XX axis of Fig. 1.;

Fig. 4 shows a shock absorber of a modified form;

Eig. ,5 shows a different modification of the hockabsor r sh wn in Fi 4; a

, Fig. ,6 shows a shock absorber ofvstill another yp ;Fig. 7 is a detail view showing another modification; and

Fig. 8 is a section on the YYaxis of Fig. 7.

Referring first to Fig. 1, at I is seen the cylinder of the shock absorber in which moves .a hollowpiston 2 constituting a closed chamber. The tightness "between the piston and the cylinder is assumed in this example by the lining 6 and a rule-c nstitutin a n the embodiment of Fig. 1 the chamber of constant volume is constituted by the inside of the hollow piston 2 and the variable yolume chamber by the bottom of cylinder l these two chambers being separated from each other by a wall 3constituting the bottom of the hollow pis ton, this wall including the various means of communication between the two chambers. ,i

p The shock absorber of the type of Fig. {1 can be of the pneumatic or hydro-pneumatic type. It will be supposed for instance in the following description that the bottom of the cylinder and the inner part of the piston to a determined level ls filled with oil, for instance, by pipe 26 ;(Flg. 1")

provided with a shutting device 27, the upper part of piston 52 being occupied by gas such as air. 'Iihe piston is shut at its upper part, for instance by .a screwed lid 4. The means of communication :between the two spaces include .as said above at least one passage controlled by a check-valve submitted to the pressure of a calibrated spring. This passageis shown at 7|, the check-valve at '8 and the spring at [8. The rod of the'check-valve isihollow as seenat 9, its upperend constituting a shown example .at ilid :4 or piston :2, this :cylinder communicating by a passage of small section 4 with the upper part oflthe-inner space of piston 2. In the lowerend off the hollow rod 9 is provided aawall 4 2 bored with a :hole l3. The inner part of chec'k-valve -8 screwed in the lower .part of rod 9 constitutes :a chamber 14 communicating :with' the face of thecheck-valve -iby holes 1 5. inside this chamber is a ball I 6 :applied against theaedge of hole 13 by a spring H. In that way when the piston thrusts in the cylinder at the la-riding shock, check-valve 8 is removed from -its :seat, the pressure due to the landing .shock overcoming the pressureof spring 4 8 :added to the pressure 10f the air-zexisting in the upper part :of the .piston and consequently in chamber I 9 situated above :rod 9 and inside this red. During the first recoilings ofthe airplane zwhenche'ckeya'lve 8icomes zbackhon its seat, the amderpressure existing 1 then under face 3 crime piston causes a suction whichx-rep.

moves :ball :lG from. its seat and which sucks the Which is inside rod .9 'Df chamber 13. Inethat way, .during :ath'etthrustingsin of the :piston, Jdetere mined bylthe roughness of the .groundon which. the .iairplane :rolls, the pressure the check valve will have1t0nvercome is no more the sum of the calibration of spring alfiandof the air pressure iin the upper :part :of the piston, but the {calibration otfzthe zpis'tcnra'dded to the reduced pressure exist ing :in'chamber .9 and J9. AS :11; has been said above, this pressure :is maintained and even :increased :during the rolling along the ground by. thcrtact that :thexslow infiltration of .air throu passage 3| I is .largelybalanced {by the suocessiye suctions of air throughthe {lower .end of th rod dnringrthe successive lzeboundings. I In-Fig. :1 has been represented also. as a exampl a balancing :devic of nr s ilreh twe h twmfacesnfthe piston stablish d acco ding ton fcaturezofthe inve tion and tak ng the p a e of the usual hole en ral-1y c ntrolled by a needle according to that arran ement. the d am er 101:} bottom 3 of thep tcn is-s a ler than h one of the inner :wall 1 f -cylind. is prov d w th a piston ri g 2' con tituted y a spl rin the endsicf whic are n -in c ntact (see also Fig. 3) Besides, the lower wall of the cylinder has an intner shape suitably profiled. The spacersituated above ring 20 communicates with the inner part oi. the piston by passages 21. v In that way the communication between the two faces of the ,p'iston 1is assumed by passages '2! and variable section passages 22 provided between the two ends of rin fzll passage which varies during the displacements of the piston i t y nd it has sa d abo e, t s b Well u derstood that the invention is not limited to the use of th "device and'that, besides, it concerns in "a special way,and independently from any'applica tion to any shock absorber ofa given type, the sai device in itself.

fjIn 1 has beenalso represented 'an arrange merit according to another feature of the invention and which can be used in some cases and this as well in fshock absorbers of the described type as in any other shock absorberof a similar type, the invention concerning also this arrangement in itself, independently from any spec'iail application.

' "This arrangement consists in the providing in bottom 3 of the pis'ton'acomplementary hole 2- 3- provided w'ith s, check-valve 24 opening flownwards and urged towards its shuttin position by el- 'spring 25. -According :to :a. preferred embodiment,this spring is calculated so as to shut the check-valve when the pressure inside the piston corresponds to the one which is determined by theaction on the shock absorber of the weight of the airplane, in such away that this checkvalve opens when the pressure overcomes, the spring. Thus when the shock absorber shortens consequently to the landing shock which increase the pressureinside theshock absorber, this one can quickly lengthen as soon as the airplane has recoiled by the fact that the pressure opens check-valve 24', this check-valve being shut only when the pressure has lowered to the value corresponding to the spring. r

In Fig. 2 has been represented a shock absorber of the same type as the one of Fig. 1 but including a few modifications of that figure, the same members are at the same reference numbers. In the example of Fig. 2, the shock absorber is provided with an arrangement con stituting another feature of the invention allowing to develop an opposing force to the spring l8 while the airplane is rolling along the ground. According to that arrangement, the end of hollow rod .9 includes a part of larger diameter 28 con stituting a second piston and engaging with a cylindrical part I00. of lid 4, the height of this cylindrical part being somewhat longer than that of the second piston 28 and being closed by a lower lid 29. Piston 28 is bored with a hole 30 and lid 29 with a hole 3|. With that arrangement, when the check-valve and the rod go down, a suction downwards still exists, determined by the underpressure which acts on ball [6 through holes l5. This underpressure occurs-in chamber 32 constituted between the second piston of. rod 9 and the upperpart of cylindrical chamber Illa. On the contrary, in space 33 situated between the bottom of piston 28 and lid 29 con tinues to exist a pressure equal to that existing in the shock absorber. Thence a push upwards applied on the whole of the annular section of part 28 situated between the inner periphery of rod 9 and the inner periphery of cylinder 10a. It can, therefore, be seen that the shock absorber becomes still more yielding than the one of Fig. 1 while the airplane rolls along the ground, though keeping the same stiffness during the landing shock.

In the example of Fig. 2, wall 3 is bored with a'hole of small section 34, taking the place of devices 29, 2|, 22 of Fig. 1. This shock absorber includes also the device 23-.-2425 intended to make easier the quick lengthening of the damper immediately after the first recoil following the landing shock. Also, there has been provided in that example a fourth passage intended to make easier the controlled shortening of the shock ab-. sorber having for instance for its purpose to precede its retraction.

This device is constituted by a passage 35 provided with a check-valve 36 submitted to the action of a compressing spring 31 which tends to remove it from its seat. During the quick displacements of the piston towards the bottom of the cylinder, due to the landing shock as well as to the shocks resulting from the roughness of the ground while the airplane is rolling along it, check-valve 36 shuts, but on the contrary it remains opened when a slow thrusting of the piston in the cylinder is caused.

It must be well understood that the use this device is optional and that besides, this latter v.canbe, applied as well inthe case of the.

8" shock absorber of Fig. 1 as in the one of the shock absorber of Fig. 2 and in a general way in any hydraulic or hydro-pneumatic shock absorber.

In the example of Fig. 4 has been represented a shock absorber ofv a different construction including also an application of the present. invention. In that example, the shock absorber is constituted by a cylinder 40 presenting a transversal' wall 4| and receiving a piston 42 which slides in its lower part. The chamber of con. stant volume isconstituted in that case by space 43 situatedabove wall 4i and the variable volume space-by. the space. situated between the wall and piston 42. In wall 4| is bored a hole 45 closed by a check-valve 46 and submitted to the pressure of a spring 66, the rod 41 of which is hollow. In that example, the outer diameter of the rod is slightly larger than the diameter of the section of the check-valve submitted to the overpressure, so that the pressure existing in'the' chamber of constant volume interferes under determined conditions in the resistance which opposes the opening of the check-valve. It must,- however, be well understood that this arrangement has been given only for an example andthat it is easy, if desired, to give the outer diameter of rod 41 the same value as the one of the section of check-valve 46 submitted to the overpressure in order to avoid any influence on the check-valve of the pressure existing in the chamber of constant volume 43. a

In the exampleof Fig. 4, rod 47 constituting a piston slides in a cylindrical part 48 which can include, if desired, means of guidingsuch as 49 constituting a tight joint. The upper part of rod li carries a piston 59 sliding in a cylinder 5!. In the building of Fig. 4, the inner space of the rod does not communicate with the space situated in chamber 52 which is situated above pis-- ton 50, a piston 53 being arranged inside the rod. This piston is urged downwards by a spring 54, its stroke downwards being limited by a shoul der 55. The communication between the upperpart of rod 47 and space 52 is provided by a hole 56 controlled by a ball 5? submitted to the action of a spring 53. This space communicates with chamber 59 situated under piston 58 by a hole 69- controlled by a ball 6! submitted to the action of a spring 62. With that disposition, whencheck-valve 46 goes down during the recoils of-' the airplane on the ground, the displacements downwards of piston 53 cause the suction of the air which is in chamber 52. On the contrary, the displacements upwards under the effect of the overpressure cause the driving back of that air in chamber 59. A substantial underpressure can thus be attained in chamber 52, an overpressure in chamber 59. Compensation holes 63 and 64 assure the 1 balancing back of the pressure of chambers 52 and 53 when the shock absorber is at rest. Wall 4! can include any other passage controlled in a suitable way, for instance of the type represented in Figs. 1 and 2. In the example of Fig. 4 has been only represented a simple hole balancing of the pressure 65.

In Fig. 5 has been represented a shock absorber of the same type as the one represented in Fig. 4, the same members being designated by the same reference numbers. The shock absorber of Fig. 5 differs from the one Fig. 4 only by the fact that piston 53 is omitted and that rod 4.1..of' check-valve 46 communicates directly with space 52v situated above piston 50 through a one-way. check-valve. .5! and with space, 59 situated under.

tialrecoils of the airplane.

amasea integral'with cylinder 16: constituting, the part-- 7 ing between the two chambers of the-shock absorber, the-space M situated above wall 12 constituting the constant. volume chamber, and the space 15- situated under this wall, the variable volume chamber; The-hole" l6, bored in wall 12, is controlled by a check-valve H the hollow rod 1% of Which slides in a cylinder 13, a spring 18a applying the check-valve on its seat. In 19 is seen the hole of small section making communicate'space 80 (situated: under rod 18 acting as a piston)- and: chamber 14: r

In- Fig. 6 has been represented besides a com plementary device constituting another feature of the=invention. This device has for purpose to determine ad'ecrease of the pressure above rod lfa of the ch'eck va'lve only'for the rather substarr For that purpose a Wall of parting 8lis provided in the lower part ofrod 18-; and bored with: an axial hole in which slides a small piston 82, the-upper part of which includes-vertical peripheral rgrooves 83 (seev also Figsrfl and: 8' in"- which; areseen the same mem bers on a bigger scale). The" piston 82 is maintained in the: closed position by a spring 85. Thus, when checkwalve l1- goesdown, piston 82 is urged by the underpressure which exists upstream the check-valve from top to bottom, but it establishes the communication between the two parts of the rod situated above and under" wall 8!, respectively, only when piston 82- has moved a determined amount.

In Figs. 7 and 8 have been represented, as it has just been said, the device with delayed action shown in Fig. 6. Besides in-Fi'g. 7 is seen another arrangement characteristic of the invention. arrangement has for its purpose to" cause a sudden suction inside the-rod; According to that feature, the body of the check-valve is provided with passages 86 establishing a communication between its inside and the chamber downstream the checkvalve; these passages being controlled by a cap 81" whichcan slide along rod 18 of the check-valve, its stroke upwards being limited by a thrust 88. Cap 81 presents a vertical edge 59. In that way, when an overpressure occurs upstream check-valve l1, cap 8l 89 goes up along rod 18 of the check-valve and uncovers holes 86. On the contrary, when the check-valve goes down, cap 87-89 goes also down and determines the shutting of holes 86 with a determined delay and suddenly. Then is created under the inner chamber of the rod a substantial underpressure which has for a result to give rise to an increased suction intended to act on the one-way checkvalve which controls the communication between the inside of the rod and the space situated above it.

It will be well understood that the arrangement which has just been described is by no means limited to its use with a check-valve with delayed action of the type represented in Fig. 7 and that, in a more general way, the various arrangements characteristic of the invention which have been represented on the different figures are by no means limited to the use with the type of shock absorber represented on this figure and that for instance the device of Fig. 7 can be used on a shock absorber represented in Figs. 1, 2, 4

, 10 and 5,. as well as check-Valves 24'- and 36 can be used withshockabsorbersof thetype represented in-Figs14, 5and6, etc.

It must also be well understood that the type of the shock absorbers, their sizes, shapes, building, etc, to which the different devices of the present invention are applied can-be of any type.

I: claim: 1

1. In a telescoping fluid shock absorber; a principal cylinder, closed at one end,-a. hollow principal piston slidably mounted in said cylinder and having closing end walls, said cylinder and said piston being adapted to contain fluid, the' inner end Wall of said piston nearest the closed end of said cylinder Jbeing apertured to provide a small communicating passage therethrough, one-way valve means mounted forclosing said passage and comprising resilient means normally urging saidvalve means into closed position, a' hollow valve stem within said hollow piston for displaceably mounting said. valve means, said valve stem being provided with a small aperture defining a: restricted communication channel between the interior of said valve stem and the exposed "face of said valve means engageable to" closesaid aperture in said: end wallofsaid principal piston,,a secondary cylinder ploscd at-bothends, mounted within the interior ofsaid hollowpiston at its end opposite said valve means, a secondary piston shell open; at one "end. and closed at the other end and-being slidably mounted within said secondary cylinder and having a closing terminal mountingxwall whereby itis mounted-on an end of said valve stem; one end wall of said" secondary cylinder being apertured for slidably receiving said valve "stem, and said terminal mounting wall being further provided: with a small aperture providing communication between the interior of said secondary piston shell and the interior of said secondary cylinder on the mounting stem" side of said mounting wall, the wall ofsaid secondary cylinder being provided With a'restricted aperture providing communication between the portion of the interior of said secondary cylinder nearest the end ofsaid valve stem carrying said valve means; and the interior of said principal.

piston. v

a telescoping fluid shock absorber -a principal cylinder adapted to contain fluid and divided by a transversal wall having a valve seat into a first chamber and a second chamber, a piston slida'ble within said first chamber, a secondary cylinder mounted within said second chamber, integral with the end wall of said second chamber remotest from said transversal wall and whose end wall nearest said transversal wall is apertured, a valve stem slidably mounted through said apertured end wall of said auxiliary cylinder, said valve stem being provided, at its end remotest from said transversal wall, with a piston slidable within said secondary cylinder and, at its end nearest said transversal wall, with a first apertured valve means, adapted to be pressed against said valve seat, resilient means for normally urging said valve stem from said auxiliary cylinder against said valve seat, an auxiliary piston slidably mounted within said hollow valve stem, auxiliary resilient means normally urging said auxiliary piston against a seatin the inner peripheral wall of said valve stem, a second valve mean providing a restricted communication between the portion of the interior of said valve stem above the end of said auxiliary piston remote from said seat, and the portion of the interior of said secondary cylinder remote from the end of said valve stem carrying said second valve means, a third valve means providing a restricted communication between the portion of the interior of said valve stem above the end of said auxiliary piston remote from said seat, and the portion of the interior of said secondary cylinder nearest the end of said valve stem carrying said second valve means,

3.'In a telescoping fluid shock absorber, a principal cylinder, closed at one end, a hollow principal piston slidably mounted in said cylinder and having closing end walls, said cylinder and said piston being adapted to contain fluid, the inner end wall of said piston nearestthe closed end of said cylinder being apertured to provide a small communicating passagetherethrough, one-way valve means mounted for closing said passage and comprising'resilie'nt means,

normally urging said valve means into closed position, a secondary cylinder, mounted within the interior of said'hollow piston at its end oppo site said valve means, a hollow valve stem within said hollow piston, being slidably 'mounted'within said secondary cylinder, for displaceably mounting said valve means, and provided with a small 'aperture defining 'a restricted communication channel'bet'ween the interior of said valve stem and the exposed face ofsaid valve means, said secondary cylinder being provided with a small aperture defining a communicating channel between the interior of said secondary cylinder and the interior of said principal piston.

4. In a fluid shock absorber, a variable-volume chamber, a constant-volume chamber, a wall provided with a valve seat for separating said chambers, a cylindrical chamber made integral with said constant-volume chamber and open at its end facing said wall, valve mean s'mounted within said constant-volume chamber, the front part of said valve means beingadap'ted to close said valve seat and the back part of said valve means beingslidably mounted within said cylindrical chamber, a spring normally urging said front part of said valve means against said valve seat, and means for lowering the pressure obtaim'ng within said cylindrical chamber when the pressure obtaining within said variable-volume chamber is decreasing andfor withstanding the increase of pressure within said cylindrical champiston slidable within said first chamber, a secondary cylinder mounted within said second chamber, integral with the end wall of said sec ond chamber remotest from said transversal wall and whose end wall nearest said transversal wall is apertured, a valve stem slidably mounted through said apertured end wall of said secondary cylinder, said valve stem being provided at its end remotest from said transversal wall, with a piston slidable within said secondary cylinder and at its end nearest said transversal wall with a first apertured valve means, adapted to be pressed against said valve seat, resilient means for normally urging said valve stem from said auxiliary cylinder against said valve seat, a second valve means providing a restricted communication between the portion of the interior of said valve stem remote from said transversal WalL'and the portion of the interior of said secondary cylinder remote from said transversal wall, and a third valve means providing a restricted communication between the portion of the interior of said valve stem remote from said transversal wall, and the portion of the interior of said secondary cylinder nearest said transversal Wall.

JEAN MERCIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,155,605 Levy Apr. 25, 1939 2,186,011 De Port Jan. 9, 1940 2,333,096 Dowty Nov. 2, 1943 FOREIGN PATENTS Number Country Date 7 408,592 Great Britain Apr. 5, 1934 826,293 France Mar. 28, 1938 

